Highly efficient and aberration-corrected spectrometer for advanced Raman spectroscopy

We designed an asymmetric Czerny-Turner-type spectrometer with a spectral resolution of approximately 1 cm(-1) and a focal length of 500 mm (F/4.1) to improve the aberration properties: (1) coma aberration was corrected by use of a particular incident angle for a condensing mirror based onShafer's equation, (2) astigmatism was corrected by use of a toroidal condensing mirror, (3) the optimum distance was found between a grating and condensing mirror so that the centered light and marginal light at the detector possess the same incident angles to the condensing mirror (the aberration is therefore excellently corrected over the whole detector surfaces), and (4) these optimal configurations are ensured in a wide wavelength between 400 and 800 nm by use of gratings with different grooves. Then the spectrometer was constructed, and the excellent optical properties were confirmed with aligned fiber images and Raman spectra from copper phthalocyanine.